The present invention relates to frictionless transport of a load, and a method and apparatus for achieving such transport.
Frictionless transport of objects is a desirable goal in a number of commercial settings. In particular, in a clean-room setting where manufactured objects such as magnetic discs and wafers are being moved from one processing station to another, it is desirable to minimize generating dust or other particles during the any part of the clean-room operation. One source of such particles is from frictional contact between elements in a conventional transport device.
Frictionless movement of an object may also be desirable in machines of other mechanical devices where rapid and repeated mechanical movements can cause mechanical failure in one or more parts of the apparatus.
The invention includes, in one aspect, a frictionless transport apparatus for transporting an object of load from a first to a second station or position. The apparatus includes a frame extending between the first and second stations and a carriage mounted for movement along said frame, in a levitated condition, while carrying a load between the first and second stations. The carriage and object are suspended or partially suspended by frame and carriage biasing magnets mounted on the frame and carriage, respectively. The carriage is stabilized in its suspended condition by a stabilizing structure that includes a magnetic array extending between the first and second stations on the frame, and a diamagnetic plate mounted on said carriage, with at least a portion of the plate confronting and being disposed proximate to at least a portion of the array, as the carriage moves along said track. Magnetic interaction between said diamagnetic plate and the magnetic array acts to resist movement of the plate toward the array. The carriage in its levitated condition is moved along the frame by a frictionless drive system, such as a linear electromagnetic or electrostatic system or a pneumatic system.
The biasing magnet on the frame may be an electromagnet, where the strength of the magnetic field produced by the magnet can be varied to match carriage and load weight, or may be a permanent magnet, where load variation may be accommodated by diamagnetic interactions, or a adjusted distance between the biasing magnets.
The magnetic array may be, in various embodiments, (i) a planar array composed of magnets arranged side-by-side in alternating polarity, (ii) a planar array composed of magnets arranged side-by-side in alternating vertical and horizontal magnetic pole orientation, with the vertically-oriented magnets alternating in polarity and the horizontally-oriented magnets alternating in polarity, or (iii) an array formed of a plate of isotropic material that is magnetized with alternating poles.
In a preferred embodiment, the stabilizing structure includes at least two spaced-apart magnetic arrays, and the diamagnetic plate has opposite faces, at least portions of which confront and are proximate to at least a portion of the spaced apart magnetic arrays. Magnetic interaction between the diamagnetic plate and each planar array acts to maintain the plate between, and spaced from, the arrays. The spaced-apart arrays may be formed, for example, by a plurality of spaced-apart arrays supported by and projecting from a base member. The magnetic arrays and diamagnetic plate disposed between the arrays may be planar and substantially horizontally disposed, or planar and substantially vertically disposed.
The diamagnetic plate may be composed of graphite, e.g., pyrolytic graphite, or bismuth. The device may further include a conductive plate carried on the carriage, for moving therewith proximate to and adjacent the magnetic array, as the carriage moves along said frame, to damp eddy currents formed by carriage movement along the frame.
In one embodiment, the carriage""s biasing magnet includes a linear array of magnets separated from each other by a known spacing distance, and the drive system includes a conductive-wire path and an alternating current source connected to the wire path for producing a linear magnetic drive force on the linear array of biasing magnets. In another embodiment, the drive system operates by electrostatic attraction between electrostatic elements on the frame and carriage, as the carriage moves along the frame. In yet another embodiment, the drive system operates by applying a compressed gas stream to the carriage from the frame, as the carriage moves along the frame.
In another aspect, the invention includes a method of frictionless transport of a load between first and second stations. The method includes the steps of placing the load on a carriage, supporting a substantial portion of the weight of the carriage and load with biasing magnets carried on a frame extending between the first and second stations and on the carriage, stabilizing the position of the carriage in a levitated condition, as it moves along the frame, by magnetic forces produced between a diamagnetic plate on the carriage and a magnetic array extending between the first and second stations on the frame, and driving the carriage along the frame with a frictionless drive system.
In another aspect, the invention includes a levitated system in which the levitated object is levitated with a gap of up to 5-10 mm or more. The system includes a frame and supported object, e.g., carriage, having biasing magnets for supporting a significant part of the weight of the object, and stabilizing structure includes a magnetic array on the frame and a diamagnetic plate on the object, for stabilizing the object in its levitated condition. The system may serve, for example, as a frictionless bearing in a machine, or a novelty item with an easily observable levitation gap.
These and other objects and features of the invention will be more fully appreciated when the following detailed description of the invention is read in conjunction with the accompanying drawings.